JPS60132077A - Disconnection detecting apparatus for engine preheater - Google Patents

Abstract

PURPOSE:To detect the disconnection of a glow plug, etc. and the fusion of a current control element by installing a conduction circuit consisting of the current control element and a preheater which are connected in series and a logic circuit for generating an output in correspondence with the output of a driving circuit and the potential of the connection point. CONSTITUTION:A relay 4 as current control element and an electrical heater 7 for heating the inhaled air for an engine are connected in series. When the electrical heater 7 is burnt-out, a heater terminal 6 is opened, and a transistor 33 is put OFF, and then a collector terminal 38 and a base terminal 39 are put into ''H'' level, and a transistor 37 is put ON, and an indication lamp 8 comes ON. When the contact of the relay 4 is fused after the completion of conduction, the heater terminal 6 is always at ''H'' level, and the transistor 33 is put OFF, and the transistor 37 is put ON, and the indication lamp 8 comes ON. Therefore, the disconnection of the glow plug, etc. and the fusion of the current control element can be detected by one detection signal.

Description

[Detailed Description of the Invention] [Field of Industrial Application] The present invention is applied to a preheating device such as a diesel engine equipped with a glow plug or an electric heater that warms intake air (hereinafter referred to as a glow plug, etc.). The present invention relates to a device for detecting wire breakage such as the like.

(Objective of the Invention) The object of the present invention is to (1) determine the presence or absence of disconnection and a method for supplying current to the glow plug, etc. without changing the circuit constants depending on whether the glow plug, etc. is energized or not; It is possible to detect the presence or absence of welding of contacts (for example, relays).

[Summary of the structure of the invention]

The present invention has the structure described in the claims, so that the contact signal of a glow plug, etc. (“H” when energized, “L” when not energized) and the energization drive signal (“H” when driven, “H” when driven, For example, by taking the exclusive OR of ``L'' (if not energized), the exclusive OR output becomes ``H'' if it is not energized even though it is being driven. If so, the exclusive OR output becomes "H", that is, the contacts are welded, and the second objective is achieved.

〔Example〕

In the embodiment of the present invention shown in FIG. 1, 1 is an in-vehicle battery, 2 is an ignition key switch, and 3 is an electric heater energization controller including a disconnection detection circuit of the present invention. (2) A known control circuit 31 for controlling energization is provided. 32 is a relay driving transistor;
33 is an amplification transistor of the transistor 32.

The diode 34, the diode 36, and the resistor 35 are a logic circuit whose inputs are the cathodes of the diodes 34 and 36. 37 is a transistor for driving a disconnection indicator lamp; 6 is an electric heater terminal; 7 is an electric heater for heating intake air of the engine; and 8 is a disconnection and contact welding indicator lamp. Reference numeral 38 is the collector terminal of the transistor 32, and when the relay 4 is driven, the 1-transistor 33 is on, so it is at the "L" level. 39 This is the base terminal of the transistor for driving the indicator lamp for broken wires and welded contacts.

The operation of the above configuration will be described. When the ignition switch 2 is closed, the ON relay 4 of the transistors 33 and 32 is closed by the control circuit 31, and energization of the electric heater 7 is started. By energizing the electric heater 7, the heater terminal 6 goes to "I" level, but since the transistor 33 turns on, the collector terminal 38 goes to "L" level.
Therefore, the base terminal 39 becomes "L" level and the transistor (
3) The switch 37 is OFF and the indicator lamp 8 does not light up.

Next, when the control circuit 31 outputs a signal indicating the end of energization, the transistors 33 and 32 are turned off, and the relay 4 is turned off.
F or the transistor 33 is OFF, the collector terminal 38 becomes "H" level, but the heater terminal 6 is grounded via the low resistance electric heater 7, so the base terminal 39 becomes "H" level via the diode 36. When the level is L'', the transistor 37 is OFF and the indicator lamp 8 does not light up.

If the electric heater 7 is disconnected, the heater terminal 6 is not grounded through the electric heater and becomes an oven, and since the transistor 33 is OFF, the collector terminal 38 becomes "H".
The base terminal 39 becomes "H" level, the transistor 37 is turned on, and the display lamp 6 is turned on.

Furthermore, when the contacts of the relay 4 are welded after energization, the heater terminal 6 is always at the "H" level, and since the transistor 33 is OFF, the collector terminal 38 is at the "H" level and the base terminal 39 is at the "H" level. 37 is O
N Therefore, display (4) Number 8 lights up.

In the second embodiment of the present invention shown in FIG.
6, 8.32, 33, and 37.39 are the same as the parts shown with the same symbols in FIG. 1, respectively.

3A is a glow plug energization controller including a disconnection detection circuit of the present invention, and has a control circuit 31A that controls energization to the coil of relay 4, which is a current control element. 7A is a glow plug connected in parallel for the number of cylinders (4 cylinders), 6A is a glow plug terminal, 51 is the emitter side to the glow plug terminal 6 of the relay 4, the base 52 is a resistor, and the coil excitation terminal of the relay 4 via a diode. The collector 39 is connected to the base of the transistor 37, forming a logic circuit in which the base terminal 52 and the emitter terminal are input, and the collector terminal 39 is the main input.

The operation of the above configuration will be described. When the ignition switch 2 is closed, the ON relay 4 of the transistors 33 and 32 is closed by the control circuit 31A, and energization of the glow plug 7A is started. When the glow plug 7A is energized, it glows (5).The plug terminal 6A becomes "H" level, but the transistor 3
The collector terminal of 2, that is, the excitation terminal of relay 4 is “H”
Therefore, the base terminal 52 is at the "H" level, so the transistor 51 is OFF, and the base terminal 39 is at the "L" level.
level, the transistor 37 is OFF and the indicator lamp 8
does not light up.

Next, when the control circuit 31A outputs a signal to end the energization, the transistors 33 and 32 are turned OFF and the relay 4 is turned OFF.
Becomes FF. Since the transistor 32 is OFF, the base terminal 52 and the resistor 52 are grounded through the diode excitation coil and go to "L" level, turning the transistor 51 ON.
shall be. However, since the relay 4 is OFF, the glow plug terminal 6A is grounded through the low resistance glow plug 7A, so the base terminal 39 becomes "L" level, the transistor 37 is OFF, and the indicator lamp 8 does not light up. If the four glow plugs 7A are disconnected, the glow plug terminal 6A is not grounded through the glow plug 7A and becomes open, and since the transistor 51 is ON, the base terminal 39 becomes (6) "IT" level and l. The transistor 37 is turned on, so the indicator lamp 6 lights up. Furthermore, when the contacts of the relay 4 are welded after the energization ends, the glow plug terminal 6A becomes "H" level at that time, and since the transistor 32 is OFF, the base terminal 52 becomes "L" level and the transistor 51 is turned ON.
As a result, the base terminal 37 becomes "H" level, and the transistor 37 is turned on, so the indicator lamp 8 lights up.

In the embodiment of the present invention, the relay 4 as a current control element can be replaced with a power transistor to achieve the same function. Furthermore, the logic circuit may have a configuration other than that shown, and a microcomputer may also be used.

〔Effect of the invention〕

As described above, according to the present invention, disconnection of a glow plug or the like and welding of a current control element can be detected with one detection signal.

[Brief explanation of drawings]

1 and 2 are electrical wiring diagrams showing first and second embodiments of the present invention. (7) 4...Relay as current control element, 7.7A...
Electric heater and glow plug as preheater, 34°35
．． 36...Diode resistor and diode for operating the logic circuit, 51...Transistor forming the logic circuit. Representative Patent Attorney Takashi Okabe (8)

Claims (1)

[Scope of Claims] An energizing circuit in which a current control element that opens and closes in response to the output of a drive circuit and a preheater are connected in series, and a connection between the output of the drive circuit, the current control element, and the preheater. A disconnection detection device for an engine preheater, comprising: a logic circuit that generates an output under a predetermined logic condition in response to a point potential;